Blowers are used extensively in furnaces, air conditioners, and other appliances. One of the uses of particular interest here relates to the filtering or purification of air. Such blowers for air purification are usually enclosed in cabinets into which air is drawn through a front opening in the cabinet, passed through an electrostatic air cleaning and filtering system, and then discharged from the blower through an exit louver or grille. Customarily the blower is so located that the axis of rotation of the blower wheel, or rotor, extends along a horizontal axis. Air is drawn in at each end of the blower wheel and forced out centrifugally by blades, or vanes, mounted on the periphery of the blower wheel. The air drawn in by rotation of the blower wheel is discharged through a scroll-shaped, or spirally-enlarging, passage which ends at the discharge face of the blower housing.